Such a method and such a magnet holder are described in EP 2 290 217 A2. A fuel supply unit, such as a carburetor or a low pressure injection system of an internal combustion engine, includes a main body having a main air passage, which has a throttle valve mounted therein and the throttle valve includes a throttle shaft extending between two oppositely located shaft sides of the main body. A control module for the fuel supply is mounted to one of the shaft sides, which control module includes throttle position detecting means for monitoring the position of the throttle valve, and fuel valve means for controlling the fuel supply to the main air passage. The throttle position detecting means include at least one magnet or similar magnetic flux generating means, which may be mounted on a disk-shaped carrier fixed to the throttle shaft to rotate therewith, and at least one analogous Hall effect sensor or similar magnetic flux density sensing element, which may be fixed in relation to the main body of the fuel supply unit. The Hall sensor generates an output voltage that is approximately linear in relation to the size of rotation of the throttle shaft and the butterfly valve. Thus, an accurate value of the position of the throttle valve can be derived within the part throttle range. The problem of fixing the magnet or magnets reliably to the carrier is not discussed.
Several suggestions relating to the use of magnets for obtaining information about the position of the butterfly valve in a carburetor are published. U.S. Pat. No. 6,522,038 B2 discloses position sensing magnets that are fixedly mounted circumferentially about an outer surface of output shaft and extend beyond the end of output shaft to define a recess bounded circumferentially by position sensing magnets and by an end surface of output shaft at one end of the recess.
U.S. Pat. No. 7,032,617 B2 discloses an intake air control apparatus for an engine is capable of suppressing the influence of external magnetic flux from outside thereby to prevent a variation in an output of a rotational angle detection sensor due to the external magnetic flux. A permanent magnet is provided on an end portion of a shaft. A rotational angle detection sensor is disposed in a spaced parallel relation with respect to the permanent magnet, and has a magneto resistive element for detecting a change in direction of a magnetic flux of the permanent magnet thereby to detect a rotational angle of a throttle valve. A bypass member is disposed to enclose the rotational angle detection sensor with its side near the permanent magnet apertured to form an opening surface, the bypass member being made of a magnetic material which is adapted to form a bypass path for the magnetic flux from the permanent magnet. The magnet is located in a recess, but there is nothing retaining it securely in the recess.
U.S. Pat. No. 7,036,791 B2 discloses a position detection device that comprises a magnet, which is arranged at a first end of the butterfly valve shaft. The magnet is diametrically magnetized and embodied in one piece as a ring. A sensor is arranged aligned with the axis of rotation of the butterfly valve shaft, in the centre of the ring.
U.S. Pat. No. 7,111,602 B2 discloses an actuator for an intake manifold tuning valve to regulate airflow in an intake manifold of an internal combustion engine. The actuator includes a motor, control circuit, and sensor all mounted in a housing that has an opening through which an output shaft extends. The output shaft carries a driven gear for rotation of the output shaft, and a valve blade that is positioned within the intake manifold when the actuator is assembled in place. The sensor provides the control circuit with feedback data indicating the position of the valve blade and this data permits the actuator itself to provide closed loop control of the position of the valve blade using an actuator command received from the engine's electronic control unit. The driven gear has a side with a generally arcuate magnet attached thereto. The magnet is used in conjunction with the position sensor and is attached to the gear by a plurality of plastic fingers extending transversely from the side of the driven gear for receipt in through openings in a surface of the magnet. The fingers are heat staked to retain the magnet to the side of the driven gear, but the magnet is not located in a protective recess.
U.S. Pat. No. 7,210,451 B2 discloses a throttle control device that includes a motor coupled to the throttle shaft, so that the throttle valve rotates to open and close an intake air channel as the motor is driven. A detection device serves to detect the degree of opening of the throttle valve and includes a pair of arcuate magnets and a sensor. The magnets are mounted to the throttle shaft via a magnet support and are positioned to oppose each other across the rotational axis of the throttle shaft in order to produce a uniform magnetic field. The sensor is mounted to the throttle body and serves to detect a direction of the magnetic field produced by the magnets, so that the detection device outputs a signal representing the degree of opening of the throttle valve. A throttle gear has a substantially cylindrical tubular portion that is positioned to extend outward of an end surface of the throttle shaft. The tubular portion is coaxial with the throttle shaft. A yoke is formed integrally with the inner peripheral surface of the tubular portion through an insertion molding process of the tubular portion. The yoke is made of magnetic material and has a ring-shaped configuration substantially about the rotational axis of the throttle shaft. A pair of magnets and (permanent magnets) is attached to the inner peripheral surface of the yoke. The magnets are positioned to symmetrically oppose each other with respect to the rotational axis of the throttle shaft.
US 2008/0296804 A1 discloses a method of manufacturing a shaft provided with a magnet for an air flow rate adjustment valve in an internal combustion engine. The method comprises the steps of: arranging a first mold which negatively reproduces the shape of the shaft and determines the formation of a seat for the magnet; injecting a molten plastic material inside the mold in order to form the shaft provided with the seat for the magnet by injection molding; arranging a second mold which surrounds the seat for the magnet; and injecting a molten magnetic polymer in the second mold for forming the magnet by injection molding. Thus, the magnet is circular and located in a recess that is coaxial with the shaft, but there is nothing retaining it securely in the recess.
Snap-in fastening has previously been used for securing magnets in carriers but has proved to be less robust than necessary and, in addition, gluing had to be used. This is an inappropriate method for production, particularly in large numbers such as mass production. The magnets have to be secured in a way that is suitable in such production.